Methods of fabricating and coating turbine components

ABSTRACT

In one aspect, a method of forming a hot gas path component is provided. The method includes forming at least one groove in an outer surface of a substrate, wherein the at least one groove has a base and a top. The method further includes filling the at least one groove with a filler. The method also includes applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component. The filler is automatically removed from the at least one micro-channel during application of the at least one cover layer. Methods for coating a hot gas component and for assembling a turbine engine assembly are also provided.

BACKGROUND

The embodiments described herein relate generally to turbine engines, and, more specifically, to fabricating components with micro-channel cooling therein.

In a turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases. Energy is extracted from the gases in a high pressure turbine (HPT), which powers the compressor, and in a low pressure turbine (LPT), which powers a fan in a turbofan aircraft engine application, or powers an external shaft for marine and industrial applications.

Engine efficiency increases with temperature of combustion gases. However, the combustion gases heat the various components along their flow path, which in turn requires cooling thereof to achieve a long engine lifetime. Typically, the hot gas path components are cooled by bleeding air from the compressor. This cooling process reduces engine efficiency, as the bled air is not used in the combustion process.

In exemplary turbine engine components, thin metal walls of high strength superalloy metals are typically used for enhanced durability while minimizing the need for cooling thereof. Various cooling circuits and features are tailored for these individual components in their corresponding environments in the engine. For example, a series of internal cooling passages, or serpentines, may be formed in a hot gas path component. A cooling fluid may be provided to the serpentines from a plenum, and the cooling fluid may flow through the passages, cooling the hot gas path component substrate and coatings. However, this cooling strategy typically results in comparatively low heat transfer rates and non-uniform component temperature profiles.

BRIEF DESCRIPTION

In one aspect, a method of forming a hot gas path component is provided. The method includes forming at least one groove in an outer surface of a substrate, wherein the at least one groove has a base and a top. The method further includes filling the at least one groove with a filler. The method also includes applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component. The filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.

In another aspect, a method of coating a hot gas path component including a substrate with at least one groove formed in an outer surface of the substrate is provided. The method includes filling the at least one groove with a filler. The method also includes applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component. The filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.

In yet another aspect, a method of assembling a turbine engine assembly is provided. The method includes providing a turbine engine including a compressor, a combustor, and a turbine. The method also includes coupling at least one hot gas path component to the turbine engine including forming at least one groove in an outer surface of the hot gas path component. The method includes filling the at least one groove with a filler. Additionally, the method includes depositing at least one structural coating over at least a portion of the outer surface of the hot gas path component such that the at least one groove and the at least one structural coating define at least one micro-channel for cooling the hot gas path component. The filler is automatically removed from the at least one micro-channel during deposition of the at least one structural coating.

DRAWINGS

FIG. 1 is a block diagram of an exemplary rotary machine.

FIG. 2 is a schematic cross-section of an exemplary hot gas path component configuration with trapezoidal-shaped cooling channels.

FIG. 3 is a schematic cross-section of a portion of a cooling circuit of the hot gas path component of FIG. 2 with re-entrant cooling channels.

FIG. 4 is a schematic cross-section of a portion of the hot gas path component of FIG. 2 with the micro-channels filled with a filler material.

FIG. 5 is a schematic perspective view of the hot gas path component of FIG. 2 showing three micro-channels that extend partially along the surface of the substrate and channel cooling fluid to respective film cooling holes.

FIG. 6 is a schematic cross-section of one of the micro-channels of FIG. 5 showing the micro-channel conveying cooling fluid from an access hole to a film cooling hole.

Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and/or claimed in combination with any feature of any other drawing.

DETAILED DESCRIPTION

The present disclosure is directed generally to rotary machine components, particularly hot gas path components, formed with cooling features, such as micro-channels, to facilitate cooling of the respective components. In particular, aspects of the present disclosure are directed to methods of forming micro-channels in a hot gas path component for use in a turbine engine where a filler material used during formation of the micro-channels is automatically removed during the formation process.

FIG. 1 is a block diagram of an exemplary rotary machine 10, i.e., a turbomachine, and more specifically, a turbine engine. In the exemplary embodiment, rotary machine 10 is a gas turbine engine. Alternatively, rotary machine 10 is any other turbine engine and/or rotary machine, including, without limitation, a steam turbine engine. In the exemplary embodiment, turbine engine 10 includes at least one compressor 12, combustor 14, turbine 16, and fuel nozzle 20. Fuel nozzle 20 is configured to inject and mix fuel with compressed air in combustor 14. Combustor 14 ignites and combusts the fuel-air mixture and then passes hot gas flow 22 into turbine 16. Turbine 16 includes one or more stators having fixed vanes or blades, and one or more rotors having blades that rotate relative to the stators. Hot gas flow 22 passes over the turbine rotor blades, thereby driving the turbine rotor to rotate. Turbine 16 is coupled to rotatable shaft 18 where it rotates the shaft as hot gas flow 22 passes over the turbine blades. Rotatable shaft 18 may be coupled to compressor 12, as illustrated. Compressor 12 includes blades rigidly mounted to a rotor that is driven to rotate by rotatable shaft 18. As air passes over the rotating blades, air pressure increases, thereby providing combustor 14 with sufficient air for proper combustion.

Turbine engine 10 may include a plurality of hot gas path components 100 (shown in FIG. 2). Hot gas path component 100 is any component of turbine engine 10 that is at least partially exposed to a high temperature flow of gas through turbine engine 10. For example, bucket assemblies (also known as blades or blade assemblies), nozzle assemblies (also known as vanes or vane assemblies), shroud assemblies, transition pieces, retaining rings, and compressor exhaust components are all hot gas path components. It is understood, however, that hot gas path component 100 is not limited to the above examples, but may be any component that is at least partially exposed to a high temperature flow of gas. Further, it is understood that hot gas path component 100 is not limited to components in turbine engine 10, but may be any piece of machinery or component that may be exposed to high temperature gas flows.

When hot gas path component 100 is exposed to hot gas flow 22, hot gas path component 100 is heated by hot gas flow 22 and may reach a temperature at which hot gas path component 100 fails. A cooling system for hot gas path component 100 is provided to allow turbine engine 10 to operate with hot gas flow 22 at a high temperature, and to increase the efficiency and performance of turbine engine 10.

A method of coating hot gas path component 100 is described with reference to FIGS. 2-6. As indicated for example in FIGS. 3 and 4, the method includes forming one or more grooves 132 in a substrate 110. In one embodiment, multiple grooves 132 are formed in substrate 110. As indicated, for example in FIGS. 5 and 6, grooves 132 extend at least partially along an outer surface 112 of substrate 110. As indicated for example in FIG. 4, the method further includes filling grooves 132 with a filler material 120. Furthermore, as shown for example in FIG. 3, the method further includes depositing a coating 150 over at least a portion of outer surface 112 of substrate 110. More particularly, coating 150 is deposited over at least a portion of outer surface 112 of substrate 110 directly over grooves 132, whereby filler material 120 is automatically removed during the deposition process.

FIG. 2 is a schematic cross-section of an exemplary hot gas path component configuration with trapezoidal-shaped cooling channels (also referred to as re-entrant shaped cooling channels). Hot gas path component 100 includes substrate 110 with an outer surface 112 and an inner surface 116. Inner surface 116 defines at least one hollow, interior space 114. Outer surface 112 defines one or more grooves 132. Hot gas path component 100 includes a coating 150 that may include one or more layers 50. Grooves 132 and coating 150 together define a number of micro-channels 130 for cooling the hot gas path component 100. A cooling fluid may be provided to micro-channels 130 from the interior space 114, and the cooling fluid may flow through the micro-channels to cool coating 150.

Substrate 110 is typically cast prior to forming grooves 132 in outer surface 112 of the substrate. Substrate 110 may be formed from any suitable material, described herein as a “first material.” Depending on the intended application for hot gas path component 100, the first material may include Ni-base, Co-base, and Fe-base superalloys, and the like. The Ni-base superalloys may be those containing both γ and γ′ phases, particularly those Ni-base superalloys containing both γ and γ′ phases wherein the γ′ phase occupies at least 40% by volume of the superalloy. Such alloys are known to be advantageous because of a combination of desirable properties including high temperature strength and high temperature creep resistance. The first material may also include a NiAl intermetallic alloy, as these alloys are also known to possess a combination of superior properties including high temperature strength and high temperature creep resistance that are advantageous for use in turbine engine applications used for aircraft. In the case of Nb-base alloys, coated Nb-base alloys having superior oxidation resistance will be preferred, such as Nb/Ti alloys, and particularly those alloys comprising Nb-(27-40)Ti-(4.5-10.5)Al-(4.5-7.9)Cr-(1.5-5.5)Hf-(0-6)V in an atom percentage. The first material may also include an Nb-base alloy that contains at least one secondary phase, such as an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride. Such alloys are analogous to a composite material in that they contain a ductile phase (i.e. the Nb-base alloy) and a strengthening phase (i.e., an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride).

Coating 150 extends along outer surface 112 of substrate 110. Coating 150 conforms to outer surface 112 and covers grooves 132 forming channels 130. Coating 150 includes one or more layers 50. In the illustrated embodiment, coating 150 is just the first layer 50, or structural coating, that covers grooves 132. In another embodiment, a single layer may be all that is used. In alternative embodiments, however, hot gas path component 100 may include additional layers 50, such as a bondcoat and a thermal barrier coating (TBC). In one embodiment, coating 150 includes a second material, which may be any suitable material, bonded to outer surface 112 of substrate 110. For particular configurations, coating 150 has a thickness in the range of 0.1 to 2.0 millimeters, and more particularly, in the range of 0.1 to 1 millimeter, and still more particularly 0.1 to 0.5 millimeters for industrial components. For aviation components, coating 150 has a thickness in the range of 0.1 to 0.25 millimeters. However, other thicknesses may be utilized depending on the requirements for a particular hot gas path component 100.

Coating 150 may be deposited using a variety of techniques. In one embodiment, coating 150 is disposed over at least a portion of outer surface 112 of substrate 110 by performing an ion plasma deposition. Briefly, ion plasma deposition includes placing a cathode formed of a coating material into a vacuum environment within a vacuum chamber, providing substrate 110 within the vacuum environment, supplying a current to the cathode to form a cathodic arc upon a cathode surface resulting in erosion or evaporation of coating material from the cathode surface, and depositing the coating material from the cathode upon the substrate outer surface 112.

In one embodiment, the ion plasma deposition process includes a plasma vapor deposition process. Non-limiting examples of coating 150 include structural coatings, bond coatings, oxidation-resistant coatings, and thermal barrier coatings. In some embodiments, coating 150 includes nickel-based or cobalt-based alloys, and more particularly includes a superalloy, or a NiCoCrAlY alloy. For example, where the first material of substrate 110 is a Ni-base superalloy containing both γ and γ′ phases, coating 150 may include these same materials.

In other embodiments, coating 150 is disposed over at least a portion of outer surface 112 of substrate 110 by performing a thermal spray process. For example, the thermal spray process may include combustion spraying or plasma spraying, the combustion spraying may include high velocity oxygen fuel spraying (HVOF) or high velocity air fuel spraying (HVAF), and the plasma spraying may include atmospheric (such as air or inert gas) plasma spray, or low pressure plasma spray (LPPS), which is also known as vacuum plasma spray or VPS). In one embodiment, a NiCrAlY coating is deposited by HVOF or HVAF. In alternative embodiments, techniques for depositing one or more layers of coating 150 include, without limitation, sputtering, electron beam physical vapor deposition, electroless plating, and electroplating.

In one embodiment, it is desirable to employ multiple deposition techniques for forming coating 150. For example, with reference to FIG. 3, first layer 54 may be deposited using an ion plasma deposition, and second layer 56 and optional additional layers (not shown) may be deposited using other techniques, such as a combustion spray process (for example HVOF or HVAF) or using a plasma spray process, such as LPPS. Depending on the materials used, the use of different deposition techniques for the coating layers 50 may provide benefits in strain tolerance and/or in ductility.

More generally, the second material used to form coating 150 includes any suitable material that permits hot gas path component 100 to function as described herein. In one embodiment of hot gas path component 100, the second material is capable of withstanding temperatures of approximately 1150° C., while the TBC can withstand temperatures of approximately 1320° C. Coating 150 is compatible with and adapted to be bonded to outer surface 112 of substrate 110. This bond may be formed when coating 150 is deposited onto substrate 110. Bonding may be influenced during the deposition by many parameters, including the method of deposition, the temperature of substrate 110 during the deposition, whether the deposition surface is biased relative to the deposition source, and other parameters. Bonding may also be affected by subsequent heat treatment or other processing. In addition, the surface morphology, chemistry, and cleanliness of substrate 110 prior to the deposition can influence the degree to which metallurgical bonding occurs. In addition to forming a strong metallurgical bond between coating 150 and substrate 110, it is desirable that this bond remain stable over time and at high temperatures with respect to phase changes and interdiffusion, as described herein. By compatible, it is preferred that the bond between these elements be thermodynamically stable such that the strength and ductility of the bond do not deteriorate significantly over time (e.g., up to 3 years) by interdiffusion or other processes, even for exposures at high temperatures of approximately 1,150° C. for a Ni-base alloy substrate 110 and Ni-base coating 150, or higher temperatures of approximately 1,300° C. where higher temperature materials are utilized, such as Nb-base alloys.

In one embodiment where the first material of substrate 110 is an Ni-base superalloy containing both γ and γ′ phases or a NiAl intermetallic alloy, second materials for coating 150 may include these same materials. Such a combination of coating 150 and substrate 110 materials is preferred for applications where the maximum temperatures of the operating environment are below 1650° C. In an embodiment where the first material of substrate 110 is an Nb-base alloy, second materials for coating 150 may also include an Nb-base alloy, including the same Nb-base alloy.

In some embodiments, such as applications that impose temperature, environmental, or other constraints that make the use of a metal alloy coating 150 undesirable, it is preferred that coating 150 include materials that have properties that are superior to those of metal alloys alone, such as composites in the general form of intermetallic compound (I_(S))/metal alloy (M) phase composites and intermetallic compound (I_(S))/intermetallic compound (I_(M)) phase composites. Metal alloy M may be the same alloy as used for substrate 110, or a different material, depending on the requirements of hot gas path component 100. These composites are, in general, similar in that they combine a relatively more ductile phase M or I_(M) with a relatively less ductile phase I_(s), in order to create coating 150 with the advantages of both materials. Further, in order to have a successful composite, the two materials must be compatible. As used herein in regard to composites, the term “compatible” means that the materials must be capable of forming the desired initial distribution of their phases and maintaining that distribution for extended periods of time, as described above, at temperatures of 1,150° C. or greater without undergoing metallurgical reactions that substantially impair the strength, ductility, toughness, and other important properties of the composite. Such compatibility can also be expressed in terms of phase stability. That is, the separate phases of the composite should be stable during operation at operating temperature over extended periods so that the phases remain separate and distinct, retaining their separate identities and properties, and do not become a single phase or a plurality of different phases due to interdiffusion. Compatibility can also be expressed in terms of morphological stability of the interphase boundary interface between the I_(S)/M or I_(S)/I_(M) composite layers. Such instability may be manifested by convolutions that disrupt the continuity of either layer. It is also noted that within a given coating 150, a plurality of I_(S)/M or I_(S)/I_(M) composites may also be used, and such composites are not limited to two material or two phase combinations. The use of such combinations is merely illustrative, and not exhaustive or limiting of the potential combinations. Thus M/I_(M)/I_(S), M/I_(S1)/I_(S2) (where I_(S1) and I_(S2) are different materials), and many other combinations are possible.

In an embodiment where substrate 110 includes an Ni-base superalloy comprising a mixture of both γ and γ′ phases, I_(S) may include Ni₃ [Ti, Ta, Nb, V], NiAl, Cr₃Si, [Cr, Mo]_(x)Si, [Ta, Ti, Nb, Hf, Zr, V]C, Cr₃C₂, and Cr₇C₃ intermetallic compounds and intermediate phases, and M may include an Ni-base superalloy comprising a mixture of both γ and γ′ phases. In Ni-base superalloys comprising a mixture of both γ and γ′ phases, the elements Co, Cr, Al, C, and B are nearly always present as alloying constituents, as well as varying combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the constituents of the exemplary I_(S) materials described correspond to one or more materials typically found in Ni-base superalloys as may be used as the first material (to form substrate 110), and thus may be adapted to achieve the phase and interdiffusional stability described herein. As an additional example in the case where the first material (substrate 110) includes NiAl intermetallic alloy, I_(s) may include Ni₃ [Ti, Ta, Nb, V], NiAl, Cr₃Si, [Cr, Mo]_(x)Si, [Ta, Ti, Nb, Hf, Zr, V]C, Cr₃C₂, and Cr₇C₃ intermetallic compounds and intermediate phases and I_(M) may include a Ni₃Al intermetallic alloy. Again, in NiAl intermetallic alloys, one or more of the elements Co, Cr, C, and B are nearly always present as alloying constituents, as well as varying combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the constituents of the exemplary I_(S) materials described correspond to one or more materials typically found in NiAl alloys as may be used as the first material, and thus may be adapted to achieve the phase and interdiffusional stability described herein.

In an embodiment where substrate 110 includes an Nb-base alloy, including an Nb-base alloy containing at least one secondary phase, I_(S) may include an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride, and M may include an Nb-base alloy. It is preferred that such I_(S)/M composite includes an M phase of an Nb-base alloy containing Ti such that the atomic ratio of the Ti to Nb (Ti/Nb) of the alloy is in the range of 0.2-1, and an I_(S) phase comprising a group consisting of Nb-base silicides, Cr₂ [Nb, Ti, Hf], and Nb-base aluminides, and wherein Nb, among Nb, Ti and Hf, is the primary constituent of Cr₂ [Nb, Ti, Hf] on an atomic basis. These compounds all have Nb as a common constituent, and thus may be adapted to achieve the phase and interdiffusional stability.

In addition to coating system 150, the interior surface of groove 132 (or of the micro-channel 130, if the first layer of coating 150 is not particularly oxidation resistant) can be further modified to improve its oxidation and/or hot corrosion resistance. Suitable techniques for applying an oxidation-resistant coating (not shown) to the interior surface of grooves 132 (or of micro-channels 130) include vapor-phase or slurry chromiding, vapor-phase or slurry aluminizing, or overlay deposition via evaporation, sputtering, ion plasma deposition, thermal spray, and/or cold spray. Example oxidation-resistant overlay coatings include materials in the MCrAlY family (M={Ni, Co, Fe} and Y={yttrium or another rare earth element}) as well as materials selected from the NiAlX family (X={Cr, Hf, Zr, Y, La, Si, Pt, Pd}).

FIG. 3 is a schematic cross-section of a portion of a cooling circuit of the hot gas path component of FIG. 2 with re-entrant cooling channels. As illustrated, base 134 of each groove 132 is wider than top 136 forming a trapezoidal-shaped (or re-entrant shaped) groove. To facilitate the deposition of coating 150 over groove 132 and the automatic removal of the filler during the deposition process, it is desirable to have base 134 of groove 132 to be larger than top 136 of groove 132. This also permits the formation of a sufficiently large micro-channel 130 to meet the cooling requirements for hot gas path component 100. In some embodiments, base 134 of a respective one of the re-entrant shaped grooves 132 is at least 2 times wider than top 136 of the respective groove 132. For example, if base 134 of groove 132 were 0.6 millimeters, top 136 would be less than 0.3 millimeters in width. In alternative embodiments, base 134 of the respective re-entrant shaped groove 132 is at least 3 times wider than top 136 of the respective groove 132, and more particularly, base 134 of the respective re-entrant shaped groove 132 is in a range of approximately 3-4 times wider than top 136 of the respective groove 132. Beneficially, a large base to top ratio increases the overall cooling volume for micro-channel 130, while facilitating the deposition of coating 150 over groove 132 and the automatic removal of the filler during the deposition process.

Additionally, it is desirable to limit the depth of groove 132 in order to facilitate the automatic removal of the filler during the deposition process, wherein the depth is defined as the distance between the base of the groove and outer surface 112 of substrate 110. By forming the re-entrant shaped grooves 132 with a depth in the range of approximately 0.5 mm to approximately 1.27 mm (0.020 inches to 0.050 inches), the filler can be automatically removed during the coating application process, thereby eliminating the difficult filler removal processing step for conventional micro-channel forming techniques.

In addition, by forming re-entrant shaped grooves 132 with narrow openings 136 (tops) in the range of approximately 0.127 mm to approximately 0.4 mm (0.005 inches to 0.016 inches), openings 136 can be bridged by coating 150 and the filler can be automatically removed during the coating application process, thereby eliminating the difficult filler removal processing step for conventional micro-channel forming techniques. In the embodiment illustrated, coating 150 completely bridges grooves 132, such that coating 150 seals micro-channels 130.

As discussed above, although micro-channels 130 are shown as re-entrant shaped micro-channels, micro-channels 130 may have any configuration, for example, they may be straight, curved, or have multiple curves, etc. For the example, in one embodiment, the grooves are rectangular shaped. Specifically, base 134 of each of grooves 132 is substantially the same width as top 136 of groove 132. In some embodiments, openings 136 (tops) are in the range of approximately 0.127 mm to approximately 0.4 mm (0.005 inches to 0.016 inches), whereby openings 136 can be bridged by coating 150. In addition, the depth of grooves 132 may be in the range of approximately 0.5 mm to approximately 1.27 mm (0.020 inches to 0.050 inches), whereby filler material 120 can be automatically removed during the coating application process, thus eliminating the difficult filler removal processing step for conventional micro-channel forming techniques.

FIG. 4 is a schematic cross-section of a portion of hot gas path component 100 of FIG. 2 with micro-channels 130 filled with a filler material. In an exemplary embodiment, each groove 132 may be filled with a filler material 120 that is automatically removed during the application process of coating 150 to substrate 110. The filler can be one of several materials that can withstand initial exposure to the velocity and temperature conditions of coating 150 application processes described above. Filler material 120 is then automatically removed as vapor during the complete coating process. In an exemplary embodiment, filler material 120 is a silicone-based polymer elastomer comprising methyl vinyl/di-methyl vinyl/vinyl terminated siloxane (20%-30%), vinyl silicone fluid (20%-30%), ground silica (15%-30%), silicon dioxide (15%-25%), and silanol terminated polydimethylsiloxane (PDMS) (3%-9%), where the percentages are in weight. An example of such a material is MACHBLOC™, commercially available from Tapeworks of Bethlehem, Pa. In another embodiment, the silicone-based polymer filler material 120 may be HVMC™, commercially available from Green Belting Industries, of Mississauga, Ontario, Canada. Filler material 120 may be applied as putty-like filler that deforms easily into any channel or hole, or can be formulated into a slurry type consistency to be brushed into grooves 132.

The primary benefit of using filler material 120 described above to fill grooves 132 is that filler material 120 is automatically removed as vapor during the complete coating process. A benefit beyond automatic removal is that the filler can withstand the initial impact velocity and the temperature of coating 150, whereby enough filler remains in grooves 132 to assure that no coating 150 collects in grooves 132.

After application of filler material 120 to grooves 132, outer surface 112 of substrate 110 may be cleaned and prepared for coating, such as by machining, grit blasting, washing, and/or polishing outer surface 112, including the portions of filler material 120 that form or extend past outer surface 112. Once outer surface 112 of substrate 110 is suitably cleaned and prepared, one or more surface coatings may be applied to outer surface 112 over filler material 120, as depicted in FIG. 3. As described above, coating 150 may be any suitable material and is bonded to outer surface 112 of substrate 110.

FIG. 5 is a schematic perspective view of the hot gas path component of FIG. 2 showing three micro-channels that extend partially along the surface of the substrate and channel cooling fluid to respective film cooling holes. Substrate 110 and coating 150 may further define a plurality of exit film cooling holes 142. Micro-channels 130 channel the cooling fluid from the respective access hole 140 to the exiting film cooling hole 142. In one embodiment, micro-channels 130 convey the cooling fluid to exiting film cooling holes 142. Other embodiments, however, may not include a film cooling hole 142, with micro-channels 130 extending along outer surface 112 of substrate 110 and exiting off an edge of hot gas path component 100, such as the trailing edge or the bucket tip, or an endwall edge. In addition, it should be noted that although film cooling holes 142 are shown in FIG. 5 as being round, this is simply a non-limiting example. The film holes may be any shaped hole that allows film cooling hole 142 to function as described herein.

FIG. 6 is a schematic cross-section of one of the micro-channels of FIG. 5 showing the micro-channel conveying cooling fluid from an access hole to a film cooling hole. As illustrated, micro-channel 130 conveys coolant from an access hole 140 to film cooling hole 142. Typically, micro-channel 130 length is in the range of 10 to 1000 times film cooling hole 142 diameter, and more particularly, in the range of 20 to 100 times film cooling hole 142 diameter. Beneficially, micro-channels 130 can be used anywhere on outer surface 112 of hot gas path component 100. In addition, although micro-channels 130 are shown as having straight walls, micro-channels 130 can have any configuration, for example, they may be straight, curved, or have multiple curves, etc.

A method of manufacturing hot gas path component 100 is described with reference to FIGS. 2-6. As discussed above with reference to FIGS. 3 and 4, the method includes forming one or more grooves 132 in outer surface 112 of substrate 110. For the illustrated embodiments, multiple grooves 132 are formed in the substrate outer surface 112. As indicated, for example, in FIG. 2, substrate 110 has at least one hollow interior space 114. Substrate 110 is typically cast prior to forming grooves 132 in outer surface 112 of substrate 110, and example substrate materials are provided above. As discussed above with reference to FIGS. 5 and 6, each of grooves 132 extends at least partially along outer surface 112 of substrate 110 and has a base 134.

As indicated in FIG. 4, for example, the fabrication method further includes filling each of grooves 132 with filler material 120. Filler material 120 is a material that may withstand the initial velocity and temperature of coating 150, yet is automatically removed during the coating process.

As indicated in FIG. 3, for example, the fabrication method further includes depositing coating 150 over at least a portion of outer surface 112 of substrate 110 directly over grooves 132, whereby filler material 120 is automatically removed during the deposition process. Example coatings are provided above. In some embodiments, coating 150 includes at least one of a structural coating, a bond coating, an oxidation-resistant coating, and a thermal barrier coating. Coating 150 completely bridges the respective grooves 132, such that coating 150 seals the respective micro-channels 130, as indicated in FIGS. 3 and 4, for example.

In the exemplary embodiment, as shown in FIGS. 3-5, groove base 134 is wider than top 136 of the groove, such that each of grooves 132 form trapezoidal-shaped, or re-entrant shaped groove 132. Re-entrant shaped grooves 132 may be formed using one or more of abrasive liquid jet machining, plunge electrochemical machining (ECM), electrical discharge machining (EDM) with a spinning electrode (milling EDM), and laser machining (laser drilling). Re-entrant shaped grooves 132 may be formed by directing an abrasive liquid jet (not shown) at a lateral angle relative to outer surface 112 of substrate 110 in a first pass of the abrasive liquid jet, then making a subsequent pass at an angle substantially opposite to that of the lateral angle and optionally performing an additional pass where the abrasive liquid jet is directed toward base 134 of groove 132 at one or more angles between the lateral angle and the substantially opposite angle, such that material is removed from base 134 of groove 132. In this manner, a relatively narrow groove opening 136 (top of the groove) may be formed. Other tool path configurations for the jet may also be used and include any suitable tool path that permits grooves 132 to be formed as described herein. In some embodiments, a multi-axis numerically controlled (NC) tool path function may be employed to control the pivot point for the jet, to ensure a narrow opening 136. The depth of groove 132 in the exemplary embodiment ranges between approximately 0.5 mm to approximately 1.27 mm (0.020 inches to 0.050 inches) and is determined by the sweeping speed, as well as the jet travel speed along the groove when the jet pressure is set.

Exemplary embodiments of the methods for forming cooling channels are described above in detail. The methods are not limited to the specific embodiments described herein, but rather, steps of the methods may be utilized independently and separately from steps described herein. For example, the methods described herein may have other industrial or consumer applications and are not limited to practice with turbine components as described herein. Rather, one or more embodiments may be implemented and utilized in connection with other industries.

Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly stated. The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “approximately” used in connection with a quantity is inclusive of the stated value, and has the meaning dictated by context, (e.g., includes the degree of error associated with measurement of the particular quantity). In addition, the term “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, references to “one embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.

This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A method of forming a hot gas path component, the method comprising: forming at least one groove in an outer surface of a substrate, wherein the at least one groove has a base and a top; filling the at least one groove with a filler; and applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component, wherein the filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.
 2. The method in accordance with claim 1, wherein forming at least one groove in an outer surface of a substrate comprises forming the base within a range between approximately 0.5 millimeters (mm) and approximately 1.27 mm below the outer surface of the substrate.
 3. The method in accordance with claim 1, wherein forming at least one groove in an outer surface of a substrate comprises forming the width of the top within a range between approximately 0.127 mm to approximately 0.4 mm wide.
 4. The method in accordance with claim 1, wherein forming at least one groove in an outer surface of a substrate comprises forming the base wider than the top such that the at least one groove forms at least one trapezoidal-shaped shaped groove.
 5. The method in accordance with claim 4, wherein the base of the at least one trapezoidal-shaped shaped groove is at least 2 times wider than the top of the at least one trapezoidal-shaped shaped groove.
 6. The method in accordance with claim 1, wherein applying at least one cover layer comprises applying the at least one cover layer wherein the at least one cover layer completely bridges the at least one groove such that the at least one cover layer seals the at least one micro-channel.
 7. The method in accordance with claim 1, wherein applying at least one cover layer comprises performing at least one of an ion plasma deposition process, a high velocity oxygen fuel (HVOF) spray process, a high velocity air fuel (HVAF) spray process, and a low pressure plasma spray (LPPS) process.
 8. A method of coating a hot gas path component including a substrate, wherein at least one groove is formed in an outer surface of the substrate, the method comprising: filling the at least one groove with a filler; and applying at least one cover layer over at least a portion of the outer surface of the substrate, such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component, wherein the filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.
 9. The method in accordance with claim 8, wherein applying at least one cover layer comprises applying the at least one cover layer wherein the at least one cover layer completely bridges the at least one groove such that the at least one cover layer seals the at least one micro-channel.
 10. The method in accordance with claim 8, wherein applying at least one cover layer comprises performing an ion plasma deposition process.
 11. The method in accordance with claim 8, wherein applying at least one cover layer comprises performing a thermal spray process.
 12. The method in accordance with claim 11, wherein the thermal spray process is at least one of high velocity oxygen fuel (HVOF) spraying and high velocity air fuel (HVAF) spraying.
 13. The method in accordance with claim 8, wherein applying at least one cover layer comprises performing a low pressure plasma spray (LPPS) process.
 14. A method of assembling a turbine engine assembly, said method comprising: providing a turbine engine including a compressor, a combustor, and a turbine; and coupling at least one hot gas path component to the turbine engine, comprising: forming at least one groove in an outer surface of the hot gas path component; filling the at least one groove with a filler; and depositing at least one structural coating over at least a portion of the outer surface of the hot gas path component, such that the at least one groove and the at least one structural coating define at least one micro-channel for cooling the hot gas path component, wherein the filler is automatically removed from the at least one micro-channel during deposition of the at least one structural coating.
 15. The method in accordance with claim 14, wherein depositing at least one structural coating comprises depositing at least one of a nickel-based alloy and a cobalt-based alloy.
 16. The method in accordance with claim 14, further comprising heat treating the hot gas path component.
 17. The method in accordance with claim 14, further comprising applying an oxidation-resistant coating to at least one of the at least one micro-channel and the outer surface of the hot gas path component.
 18. The method in accordance with claim 14, wherein forming at least one groove in an outer surface of the hot gas path component comprises forming the at least one groove using at least one of abrasive liquid jet machining, plunge electrochemical machining (ECM), and milling electrical discharge machining (milling EDM).
 19. The method in accordance with claim 14, wherein depositing at least one structural coating comprises performing at least of an ion plasma deposition process, a high velocity oxygen fuel (HVOF) spray process, a high velocity air fuel (HVAF) spray process, and a low pressure plasma spray (LPPS) process.
 20. The method in accordance with claim 14, wherein depositing at least one structural coating comprises depositing at least one structural coating wherein the at least one structural coating completely bridges the at least one groove such that the at least one structural coating seals the at least one micro-channel. 